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AA Motoring Car Care: How run-flat tyres work

29/05/2016

Run-flat tyres could save you from a potentially dangerous situation.

Nobody wants to find themselves stuck on the side of the road, broken down, all because of a flat tyre, but several tyre manufacturers are now here to help with run-flat tyres, which allow a vehicle to continue moving, despite a loss of tyre pressure.

With so many rural roads in our country, a flat tyre can happen in the most awkward of places and sometimes it happens where there’s no safe place to pull over. So, even if you know how to change a tyre, there’s not always the opportunity to put your skills to use to help get you out of this sticky situation.

Run-flat tyres have been specially developed with reinforced tyre sidewalls and rubber clips for the rims, so you can now start to worry less about getting a flat tyre at the most inconvenient time.

If you get a puncture and your tyre has reinforced sidewalls, you can avoid the initial state of panic. These types of run flat-tyres are constructed with new rubber compounds that prevent tyre destruction with excessive flexing. This means they will continue to support the vehicle’s weight, even if the tyre has experienced a complete loss of pressure, and they can be placed on any rim, so it doesn’t matter what car you drive. These run-flat tyres are available from a variety of manufacturers such as Bridgestone, Continental, Dunlop, Goodyear and Pirelli.

The other option for run-flat tyres are rubber clips. Again these can be placed on any rim and, when fitted, they help to prevent the wheel rim from cutting into your tyre when you experience a sudden loss of tyre pressure. This type of run-flat tyre system has been developed by Michelin and is known as the PAX system.

One way to easily check whether your existing tyres are run-flats is by looking out for the universal symbol (which looks like a snail), developed by the International Organisation for Standardisation (ISO). However, this symbol is fairly new, so some manufacturers may have special branding for their older run-flat tyres, such as Bridgestone, which uses RFT, Continental, which uses SSR and Goodyear, which uses EMT.

Both run-flat tyre solutions prevent the punctured tyre from affecting the braking, acceleration and steering of your car. They usually allow you to keep travelling for up to 80km, which should get you to the nearest garage for repairs or to a safe place to pull over, from where you can then call your road service provider for assistance.

Run-flat tyres are becoming more common and it’s clear to see why when you consider their benefits. However, it’s important to note that these tyres are subject to misuse and driving on run-flat tyres for longer than the specified distance may cause your wheels to become irreparably damaged.

Those of you who are fuel-economy conscious might want to think about the 20-40 per cent weight penalty that comes with having run-flat tyres, while also increasing your car’s rolling resistance.

Some models don’t come with a spare tyre, but don’t make the mistake of assuming that it’s because the vehicle is fitted with run-flat tyres. Falling into that trap could leave you broken down at the side of the road with a puncture, regretting your wrong assumption. Avoid the situation by checking what tyres have been fitted with the dealer or owner you’re buying the car from, and keep an eye out for the ISO symbol or manufacturer’s special branding.

So, whether you’re a long-distance rural driver, you don’t know how to change a tyre, or you’re not with a road service provider, fitting your vehicle with run-flat tyres might just save the day if you ever get a puncture.

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